Soil must be tested prior to beginning any construction to ascertain the strength and the density of the soil. One method of testing the strength and the density of soil is with a dynamic cone penetrometer (DCP). The DCP testing method has been standardized by the American Society for Testing and Materials in Special Technical Publication #399 (ASTM STP-399).
Existing DCP's comprise a fifteen pound steel plate (hammer) that is slidably mounted on a steel rod, typically an “E drill” rod. The upper end of the rod is fitted with a first stationary steel ring. A second steel ring is mounted on the rod approximately twenty inches below the first steel ring. The hammer is lifted up to the upper ring and permitted to drop a height of twenty inches, at which point it impacts the lower ring, thereby driving the penetrating cone of the DCP deeper into the ground. The number of impacts required to move the cone a predetermined distance into the ground becomes an index of the strength and the density of the soil.
One problem with existing DCP's is that the two impact zones (the upper and lower steel rings that are the boundaries of the steel hammer's movement along the rod) are exposed. A user often injures a finger or a hand by catching it in the line of travel of the steel hammer during use of the DCP. A user may also be hurt by the movement of the steel hammer along the rod while transporting the DCP.
A need exists for a dynamic cone penetrometer that eliminates the potential for injuries to users while using and carrying the DCP.